Specificity of the induction of ferritin synthesis by hemin

We have previously reported that hemin derepresses ferritin mRNA translation in vitro. As noted earlier, pre-incubation of a 90 kDa ferritin repressor protein (FRP) with hemin prevented subsequent repression of ferritin synthesis in a wheat germ extract. The significance of this observation has been investigated further. Evidence is presented here that this inactivation of FRP is temperature dependent. Neither FeCl3, Fe3+ chelated with EDTA, nor protoporphyrin IX caused significant inactivation of FRP under comparable conditions, whereas Zn2(+)-protoporphyrin IX produced an intermediate degree of inhibition. The presence of a glutathione redox buffer (GSB), which was previously shown to minimize non-specific side-effects of hemin, was not necessary for the derepression reaction. Inclusion of mannitol, a free radical scavenger, did not alter the inactivation caused by hemin. Calculation of the expected ratio of hemin monomers to dimers suggests that the active species is the monomer.     

Studies in metachromatic leukodystrophy: XV. Purification of normal and mutant arylsulfatase A from human liver

In this report we describe a method to purify both normal and abnormal (inactive) arylsulfatase A. The abnormal enzyme protein was isolated both from cases of late infantile and early juvenile forms of metachromatic leukodystrophy. Conventional protein isolation methods reported earlier were followed by size exclusion high-performance liquid chromatography in the final purification stages. Both the mutant enzyme and the normal enzyme had the same HPLC elution behavior. They thus appeared to self-associate in a similar pH-dependent fashion. Both could be followed by their reaction to a rabbit antibody to normal human arylsulfatase A. The amount of homogenous protein obtained from about 500 grams of liver was 300-400 micrograms.     

RNA hydrolysis and inhibition of translation by a Co(III)-cyclen complex

Metal ion-chelator catalysts based on main-group, lanthanide, or transition metal complexes have been developed as nonenzymatic alternatives for the hydrolysis of the phosphodiester bonds in DNA and RNA. Cobalt (III), with its high-charge density, is known for its ability to hydrolyze phosphodiesters with rate constants as high as 2 x 10(-4) s(-1). We have developed a kinetically inert Co(III)-cyclen-based complex, Co(III)-cycmmb that is very potent in inhibiting the translation of RNA into protein. Contact time as short as 10 min is sufficient to achieve the complete inhibition of the translation of a concentrated luciferase RNA solution into the enzyme in a cell-free translation system. The inhibition appears to proceed through two pathways. The first pathway involves the kinetic or substitutional inertness of Co(III) for the RNA template at short contact times. This interaction is mediated through the kinetic inertness of Co(III) for the phosphate groups of the nucleotides, as well as coordination of Co(III) to the nitrogenous bases. The second pathway occurs at longer contact times and is mediated by the hydrolysis of the phosphodiester backbone. This report represents the first demonstrated use of a metal-chelate complex to achieve the inhibition of the translation of RNA into protein. This Co(III) system can be useful in its present nonsequence-specific form as a novel viral decontamination agent. When functionalized to recognize specific nucleic acid sequences, such a system could potentially be used in gene-silencing applications as an alternative to standard antisense or RNAi technologies.     

Influence of 5' proximal secondary structure on the translational efficiency of eukaryotic mRNAs and on their interaction with initiation factors

The effects of 5' proximal secondary structure in mRNA molecules on their translation and on their interaction with the eukaryotic initiation factors (eIF)-4F, eIF-4A, and eIF-4B have been examined. Secondary structures were generated in the 5' noncoding region of rabbit globin and reovirus mRNAs by means of hybridization with cDNA molecules. cDNAs hybridized to the first 15 bases downstream from the cap inhibited the translation of the mRNAs in both reticulocyte and wheat germ lysates. The degree of inhibition was directly related to the monovalent ion concentration and inversely related to reaction temperature. These hybrid structures also reduced the competitive ability of the messages. Hybrid structures beginning downstream from the first 15 bases did not inhibit the translation of beta-globin mRNA or reovirus s3 mRNA. None of the hybrid structures were detrimental to the interaction of the mRNAs with the 26-kDa cap binding protein of eIF-4F, as determined by chemical cross-linking assays. However, in the presence of ATP, hybrid structures immediately adjacent to the cap severely inhibited the cross-linking to the p46 subunit of eIF-4F or to additional eIF-4A or eIF-4B. In order to account for these observations, a two-step mechanism is proposed for the interaction of eIF-4F with the 5' end of an mRNA molecule. The first step involves a weak initial interaction of the p26 subunit with the cap. The second step requires the hydrolysis of ATP and results in the formation of a stable initiation factor-mRNA complex, which may involve eIF-4A and eIF-4B. This second step is inhibited by the presence of 5' proximal secondary structure. In any event, our results demonstrate that the effect of mRNA structure on translation rate depends strongly on its position with respect to the 5' end and that this effect is due at least in part to an inhibition of the action of initiation factors normally required for the unwinding of structure.     

Recycling of messenger RNA cap-binding proteins mediated by eukaryotic initiation factor 4B

The ability of polypeptide components of eukaryotic initiation factor (eIF) 4F to bind to the m7G cap of an mRNA, to be released from that mRNA, and then to rebind to the cap of a second mRNA has been investigated. The release and rebinding steps have been termed "recycling." It was found that eIF-4B stimulates the recycling of the 24-26 kDa (p24) component of eIF-4F, and perhaps of other components as well. By contrast, eIF-4A seemed to have little or no effect on the recycling of eIF-4F components, either in the presence or absence of eIF-4B. The recycled p24 is capable of cross-linking to oxidized cap structures. The recycled factor is also able to stimulate the cross-linking of added eIF-4A, which cross-links poorly in the absence of eIF-4F. By these criteria it seems likely that the recycled eIF-4F components are active for a second round of translational initiation.     

Upper airway chemoreflex responses to saline and water in preterm infants

Laryngeal chemoreflex (LCR) responses elicited by fluid irrigation of the larynx have been described repeatedly in animals, whereas evidence for a similar reflex in human infants is extremely limited. Using nasopharyngeal catheters to instill small volumes of warm saline or water into the pharynx, we examined the incidence and characteristics of such a reflex in nine premature infants. Saline and water elicited the same pattern of responses, which frequently included swallows, central apnea, and airway obstruction and less commonly featured coughs, prolonged apnea, and arousal. With the exception of arousal, the incidence of these responses was significantly greater after delivery of water stimuli than after saline bolus administration. We therefore deduce chemoreceptor involvement in generation of these reflex responses and propose a laryngeal site for this sensory system, as in animals. Since greater potency of water compared with saline was demonstrable in all the infants studied, we further conclude that most preterm infants possess an upper airway chemoreflex.     

Expression of CA IX in dysplasia adjacent to surgical resection margins of oral squamous cell carcinoma

Carbonic anhydrase (CA) IX is a hypoxia marker located almost exclusively in tumor cells. We analyzed the expression of this marker in dysplastic lesions adjacent to the surgical resection margin in patients with oral squamous cell carcinoma. We investigated 70 archived tumors, 36 of which showed dysplasia adjacent to the surgical margin. We used tissue microarray technology to perform an immunohistochemical study of CA IX expression. We found 12 (33.3%) cases of mild dysplasia (10 negative, 2 positive for CA IX), five (13.9%) cases of moderate dysplasia (3 negative, 2 positive for CA IX), 1 (2.8%) case of severe dysplasia (negative for CA IX) and 18 (50%) cases of carcinoma in situ (10 negative, 8 positive for CA IX). In cases of intense expression of CA IX in the tumor, the same distribution of positive and negative cases was observed in all degrees of dysplasia (mild, moderate, severe), although cases of carcinoma in situ tended to be CA IX positive.     

Remission in psoriatic arthritis: is it possible and how can it be predicted?

Introduction

Since remission is now possible in psoriatic arthritis (PsA) we wished to examine remission rates in PsA patients following anti tumour necrosis factor alpha (TNFα) therapy and to examine possible predictors of response.

Methods

Analysis of a prospective patient cohort attending a biologic clinic, between November 2004 and March 2008, was performed prior to commencing therapy and at regular intervals. Baseline clinical characteristics including demographics, previous disease-modifying antirheumatic drug (DMARD) response, tender and swollen joint counts, early morning stiffness, pain visual analogue score, patient global assessment, C reactive protein (CRP) and health assessment questionnaire (HAQ) were collected.

Results

A total of 473 patients (152 PsA; 321 rheumatoid arthritis (RA)) were analyzed. At 12 months remission, defined according to the disease activity score using 28 joint count and CRP (DAS28-CRP), was achieved in 58% of PsA patients compared to 44% of RA patients, significant improvement in outcome measures were noted in both groups (P < 0.05). Analysis of a subgroup of PsA and RA patients matched for DAS28-CRP at baseline also showed higher numbers of PsA patients achieving remission. Linear regression analysis identified the HAQ at baseline as the best predictor of remission in PsA patients (P < 0.001).

Conclusions

DAS28 remission is possible in PsA patients at one year following anti-TNF therapy, at higher rates than in RA patients and is predicted by baseline HAQ.